1. Field of the Invention
The present invention relates to an electrically conductive member capable of being used in an electrophotographic apparatus running on an electrophotographic process, such as a copy machine, a printer, a facsimile device and the like, and an image forming apparatus equipped with the electrically conductive member.
2. Description of the Related Art
As electrophotographic processes, many have been known as described in Japanese Patent Application Publication (JP-B) No. 42-23910. In general, an electrographic process includes plural steps of: electrically forming, by various means, a latent image on the surface of a photosensitive member (latent image bearing member) made from a photoconductive material; forming a toner image by developing the formed latent image with a toner; thereafter transferring the toner image on the surface of the photosensitive member, by way of an intermediate transfer member or directly, onto the surface of a transfer substrate such as paper or the like; and fixing the transferred image by heating, applying pressure, conducting hot-press, or using a solvent vapor or the like, to obtain a fixed image. The toner remaining on the surface of the photosensitive member, when required, is cleaned by means of various methods to be recycled in the above plural steps.
In an image forming apparatus for forming an image using the electrophotographic process, there have been typically adopted a contact charge type or a contact transfer type with very small generation of ozone. In such types, preferably used is a member in the shape of a roller excellent in wear-resistance and in transportability of a transfer substrate in a transfer section.
As the member in the shape of a roller, used generally is a semiconductive roller with a structure that a semiconductive elastic layer having a resistance value in the range of 1xc3x97105 to 1xc3x971012xcexa9 adjusted by addition of carbon, an ion conductive agent or the like is formed on a core metal made of stainless steel (SUS), iron or the like. Such a semiconductive roller has an elastic layer and the elastic layer is pressed to the photosensitive member or the intermediate transfer member, which is an image bearing member, to enable a nip to be formed with certainty.
In the semiconductive roller, various components are included in rubber of the elastic layer: such as residuals of a reaction initiator added in synthesis for a base polymer, a by-product accompanying the synthesis, a low molecular component of the base polymer, and a vulcanizer, softner and plasticizer added in molding of a rubber roller. If the semiconductive roller is left for a long time in press contact with a photosensitive member or an intermediate transfer member, a phenomenon occurs with ease that the components in the roller seep out on the surface of the elastic layer, which is a so-called bleeding. Most of the seeping-out components are easy to react with the photosensitive member or the intermediate transfer member, leading a problem that the components attach onto the surfaces of the photosensitive member or the intermediate transfer member to denature physical properties of the surfaces thereof via chemical reactions.
Furthermore, an elastic layer of a semiconductor roller is adjusted on its surface resistance by mechanically mixing and dispersing carbon, a metal oxide or an ion conductive agent into a rubber material and in a case where an ion conductive agent is adopted, the elastic layer not only receives a change in physical properties thereof in an environment at high temperature and high humidity, but also precipitates the ion conductive agent out on the surface thereof, thereby having resulted in a problem of a local change in surface electrical resistance value thereof. Moreover, if the semiconductive roller is left in press contact with a photosensitive member or an intermediate transfer member, there has been a case where a problem arises that the precipitated ion conductive agent contaminates the photosensitive member and the intermediate member.
In order to solve the problems, an idea comes to mind that coating is applied on the surface of an elastic layer of a semiconductive roller with a material serving as a barrier layer for preventing a component contained in the elastic layer from seeping out or precipitating on the surface thereof, whereas by the coating, the semiconductive roller is of a plural layer structure, which again produces a problem of a high cost due to increases in material cost and complexity of fabrication process.
Recently, on the other hand, in an image forming apparatus running on an electrophotographic process has come to be desired for quietness. A charging roller, one kind of semiconductive roller, produces a so-called charging sound therefrom, which is an unpleasant, offensive sound, when a high frequency AC bias is superimposed on a DC bias and reduction in such a charging sound has remained a great technical problem.
As one of methods to reduce the charging sound, a method has been proposed in which a weight is put into the interior of a photosensitive member in contact with the charging roller to prevent high frequency vibrations caused by the charging roller from propagating. However, in this method, a necessity arises for a new process that a member serving as a weight is fixed in place inside of the photosensitive member, for example a adhesion process, inevitably leading to cost-up. Moreover, as an alternative for reduction in charging sound, a method has been adopted in which a foamed layer is provided on a charging roller to absorb the vibrations. However, in this method, the material of the foamed layer is rubber and thus inevitably disables a photosensitive member in contact therewith. That is, an adverse influence therefrom as described above cannot be avoided.
Moreover, in an image forming apparatus running on an electrographic process, a long life of a photosensitive member has been desired for reduction in unit price of prints and photocopies (in other words, referred to as reduction in running cost). The surface of a charging roller in contact with a photosensitive member is, however, scraped with ease by discharge produced in a tiny gap between the photosensitive member and the charging roller, or in other words by a so-called etching phenomenon, in a case where a high frequency AC bias is superimposed on a DC bias; thereby, having lead to a problem of no realization of a long life photosensitive member.
A proposal has been made on a method that only DC bias is applied to a charging roller, in other words a so-called DC charging, as a method of reducing the charging sound and the etching phenomenon. In order to charge the charging roller in a uniform manner with such a DC charging, requirements arise for more of resistivity uniformity and a higher level surface smoothness of the charging roller as compared with requirements thus far. However, a charging roller has components contained in an elastic layer that bleeds with ease as described above and in addition, toner, paper powder and the like are attached onto the surface thereof with ease due to a conductivity thereof; therefore, the charging roller has had a problem of virtually no possibility of retaining resistance uniformity and surface smoothness with no achievement of fundamental solution of the problem.
A proposal has been made on another method for reduction in charging sound and etching phenomenon of a photosensitive member that is a new charging technique for the surface of an image bearing member, which is called injection charging, and adopted in part of apparatuses on the market. Since such a technique enables an applied DC bias to be a potential on the surface of a photosensitive member as is, no requirement arises for application of an AC bias theoretically.
The injection charging technique is, however, a technique requiring a combination of a member of a structure in which magnetic powder is held on the outer peripheral surface of a metal sleeve by the action of a magnet inside of the metal sleeve, in other words a magnetic bush charging member, and a photosensitive member with a charge injection layer, and the combination of a magnetic brush and a photosensitive member with a charge injection layer has had a weak point that any of the components is expensive.
Moreover, in the injection charge technique, a necessity arises for a higher speed rotation of a magnetic brush than that of a photosensitive member with a charge injection layer to increase in chance of charge injection. For this reason, another necessity arises for a power transmission mechanism for driving gears and a belt residing between the magnetic brush and the photosensitive member. Moreover, since a surface of a photosensitive member continues to be rubbed by metal powder as a magnetic material, naturally the surface of a photosensitive member is mechanically scraped by an abrasive action and even an imperceptible possibility exists that as deep a wound as to pass through the charge injection layer is produced in some instance.
Moreover, contaminants such as toner, paper powder and so on attach onto magnetic powder present on an outer peripheral surface of a metal sleeve to change an electrical resistance value, in company with which problematic cases occur where a charge injection ability decreases, where magnetic powder on the outer peripheral surface of a metal sleeve falls off to reduce a charge injection density and where the falling off magnetic material arrives at an image (on a paper sheet) to cause an image defect.
On the other hand, in a case where the semiconductive roller is used as transfer means or a second transfer means in an intermediate transfer method, it is requested that not only is the semiconductive roller adapted to various kinds of transfer substrates such as a thin paper sheet, a thick paper sheet, further an OHP sheet and the like, but a nip is also formed with certainty in any of a photosensitive roller and an intermediate transfer member, thereby preventing occurrence of an image defect and paper wrinkles caused by poor transportation of a transfer substrate. The requests are responded by restricting a hardness of a semiconductive roller to the lowest possible level and further, pressing down the roller deeply into a photosensitive member or an intermediate transfer member, but a problem has remained that additive amounts of a softner, a plasticizer and the like described above are forced to increase on the elastic layer; therefore bleeding occurs with more of ease to contaminate the photosensitive member or the intermediate transfer member and to produce a state easy to denature the members.
Moreover, there have been faults in semiconductive roller combined with a transfer substrate, such faults including: properties of a transfer substrate differ according to a humidity and a temperature, by which an electrical resistance value is greatly varied; and, in cases where the semiconductive roller uses a rubber material in order to obtain a low hardness as described above, properties of the semiconductive roller differ also according to a humidity and a temperature by which an electrical resistance value is greatly varied. Therefore, in a case of combination of a transfer substrate with the semiconductive roller which tend to have a great change in physical properties, a necessity arise for selecting transfer conditions according to an appropriate resistance value in each of the transfer substrate and the semiconductive roller in order to keep a constant image quality in various environments; with the result that in a prior art electrophotographic image forming apparatus, a temperature sensor and a humidity sensor were equipped therewith and a complexity control was required for feeding back detected environmental data and resistance data to determine a transfer bias.
Accordingly, the present invention has tasks to solve the problems in the prior art and to achieve the following objects. That is, it is an object of the present invention to provide an electrically conductive member capable of not only forming a desired nip with certainty, simplicity and ease at a low cost but also preventing contamination or denaturation of a photosensitive member or an intermediate member and an image forming apparatus with the electrically conductive member. Moreover, it is another object of the present invention to provide an electrically conductive member capable of reducing a charging sound and an etching phenomenon on an image bearing member and an image forming apparatus with the electrically conductive member. Furthermore, it is still another object of the present invention to provide an electrically conductive member excellent in resistance uniformity and surface smoothness and an image forming apparatus with the electrically conductive member.
The present inventor found a structure of an electrically conductive member capable of fundamentally solving the problems owned by the electrically conductive member and has reached the present invention.
The above objects can be achieved the following features of the present invention:
According to a first aspect of the present invention, there is provided an electrically conductive member, including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body in a substantially flowable state.
According to a second aspect of the present invention, there is provided an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body so as not to fill the inner volume thereof to the full.
According to a third aspect of the present invention, there is provided an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body at a fill fraction in the range of from 20 to 95% of the inner volume thereof.
According to a fourth aspect of the present invention, there is provided an electrically conductive member according to the first or second aspect, wherein the electrically conductive powder fills only from 20 to 95% of the inner volume of the cylindrical base body.
According to a fifth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to third aspects, wherein a fill fraction of the electrically conductive powder is in the range of from 50 to 95% of the inner volume of the cylindrical base body.
According to a sixth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to third aspects, wherein a fill fraction of the electrically conductive powder is in the range of from 70 to 90% of the inner volume of the cylindrical base body.
According to a seventh aspect of the present invention, there is provided an electrically conductive member according to any one of the first to sixth aspects, wherein a resistance value of the electrically conductive powder as a whole is in the range of from 10xe2x88x928 to 108xcexa9.
According to an eighth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to seventh aspects, wherein the electrically conductive powder is a mixture of different kinds of powder constituents and a resistance value of each of the powder constituents is in the range of from 10xe2x88x928 to 1017xcexa9.
According to a ninth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to eighth aspects, wherein a number average particle diameter of the electrically conductive powder is in a range of from 10 xcexcm to 1 mm.
According to a tenth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to ninth aspects, wherein the cylindrical base body comprises a magnetic material.
According to an eleventh aspect of the present invention, there is provided an electrically conductive member according to any one of the first to tenth aspects, wherein the cylindrical base body is of a layered structure.
According to a twelfth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to eleventh aspects, wherein the outer peripheral surface of the cylindrical base body comprises a deformable material which deforms due to weight of the electrically conductive powder and/or motion thereof.
According to a thirteenth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to twelfth aspects, wherein the cylindrical base body is adapted for use as a roller.
According to a fourteenth aspect of the present invention, there is provided an electrically conductive member according to any one of the first to thirteenth aspects, further including a shaft passing through the cylindrical base body in an axial direction thereof and serving as a rotation axis thereof.
According to a fifteenth aspect of the present invention, there is provided an electrically conductive member according to the fourteenth aspect, wherein the shaft is fixed by flange members provided at both ends of the cylindrical base body.
According to a sixteenth aspect of the present invention, there is provided an electrically conductive member according to the fifteenth aspect, wherein the flange members are made of an elastic material.
According to a seventeenth aspect of the present invention, there is provided an electrically conductive member according to the sixteenth aspect, wherein the electrically conductive powder contains magnetic powder.
According to an eighteenth aspect of the present invention, there is provided an image forming apparatus including an electrically conductive member according to any one of the first to the seventeenth aspect.
According to a nineteenth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; and charging means contacting the image bearing member to charge a surface of the image bearing member, wherein the charging means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body in a substantially flowable state.
According to a twentieth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; and charging means contacting the image bearing member to charge a surface of the image bearing member, wherein the charging means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body so as not to fill the inner volume thereof to the full.
According to a twenty-first aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; and charging means contacting the image bearing member to charge a surface of the image bearing member, wherein the charging means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body at a fill fraction in the range of from 20 to 95% of the inner volume thereof.
According to a twenty-second aspect of the present invention, there is provided an image forming apparatus according to any one of the nineteenth to twenty-first aspects, wherein the charging means is means applying a bias of a DC voltage or a bias generated by superimposing AC voltage on a DC voltage.
According to a twenty-third aspect of the present invention, there is provided an image forming apparatus according to any one of the nineteenth to twenty-second aspects, wherein the image bearing member and the electrically conductive member are relatively rotated about respective axes thereof by providing a differential peripheral speed therebetween.
According to a twenty-fourth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; and transfer means contacting the image bearing member to transfer a toner image on a surface thereof onto a transfer substrate, wherein the transfer means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body in a substantially flowable state.
According to a twenty-fifth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; and transfer means contacting the image bearing member to transfer a toner image on a surface thereof onto a transfer substrate, wherein the transfer means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body so as not to fill the inner volume thereof to the full.
According to a twenty-sixth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; and transfer means contacting the image bearing member to transfer a toner image on a surface thereof onto a transfer substrate, wherein the transfer means comprises an electrically conductive member including a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body at a fill fraction in the range of from 20 to 95% of the inner volume thereof.
According to a twenty-seventh aspect of the present invention, there is provided an image forming apparatus according to any one of the twenty-fourth to twenty-sixth aspects, wherein the image bearing member and the electrically conductive member are relatively rotated about respective axes thereof by providing a differential peripheral speed therebetween.
According to a twenty-eighth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; charging means contacting the image bearing member to charge a surface thereof; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein at least one of the charging means, the first transfer means and the second transfer means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body in a substantially flowable state.
According to a twenty-ninth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; charging means contacting the image bearing member to charge a surface thereof; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein at least one of the charging means, the first transfer means and the second transfer means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body so as not to fill the inner volume thereof to the full.
According to a thirtieth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; charging means contacting the image bearing member to charge a surface thereof; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein at least one of the charging means, the first transfer means and the second transfer means comprises an electrically conductive member including a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body at a fill fraction in the range of from 20 to 95% of the inner volume thereof.
According to a thirty-first aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; charging means contacting the image bearing member to charge a surface thereof; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein at least one of the charging means, the first transfer means and the second transfer means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body in a substantially flowable state and the electrically conductive powder includes magnetic powder, the image forming apparatus further including: magnetic field forming means forming a magnetic field in which the electrically conductive powder is attracted to the image bearing member or the intermediate transfer member.
According to a thirty-second aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; charging means contacting the image bearing member to charge a surface thereof; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein at least one of the charging means, the first transfer means and the second transfer means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body so as not to fill the inner volume thereof to the full and the electrically conductive powder includes magnetic powder, the image forming apparatus further including: magnetic field forming means forming a magnetic field in which the electrically conductive powder is attracted to the image bearing member or the intermediate transfer member.
According to a thirty-third aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; charging means contacting the image bearing member to charge a surface thereof; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein at least one of the charging means, the first transfer means and the second transfer means comprises an electrically conductive member including a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body at a fill fraction in the range of from 20 to 95% of the inner volume thereof and the electrically conductive powder includes magnetic powder, the image forming apparatus further including: magnetic field forming means forming a magnetic field in which the electrically conductive powder is attracted to the image bearing member or the intermediate transfer member.
According to a thirty-fourth aspect of the present invention, there is provided an image forming apparatus according to any one of the thirty-first to thirty-third aspects, wherein the magnetic field forming means is a film having magnetism provided on an inner peripheral surface of the image bearing member or the intermediate transfer member.
According to a thirty-fifth aspect of the present invention, there is provided an image forming apparatus according to any one of the thirty-first to thirty-third aspects, wherein the magnetic field forming means is a magnetic force generating member provided at a position opposite the electrically conductive member on an inner peripheral section of the image bearing member or the intermediate transfer member.
According to a thirty-sixth aspect of the present invention, there is provided an image forming apparatus according to any one of the thirty-first to thirty-third aspects, wherein the image bearing member or the intermediate transfer member includes a base body made of a magnetic material and the magnetic field forming means is the base body.
According to a thirty-seventh aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member in the shape of an endless belt; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein the second transfer means is an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body in a substantially flowable state and the electrically conductive powder includes magnetic powder, the image forming apparatus further including: magnetic field forming means forming a magnetic field in which the electrically conductive powder is attracted to a support member provided at a position opposite the second transfer means on an inner peripheral section of the intermediate transfer member.
According to a thirty-eighth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member in the shape of an endless belt; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein the second transfer means comprises an electrically conductive member including: a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body so as not to fill the inner volume thereof to the full and the electrically conductive powder includes magnetic powder, the image forming apparatus further including: magnetic field forming means forming a magnetic field in which the electrically conductive powder is attracted to a support member provided at a position opposite the second transfer means on an inner peripheral section of the intermediate transfer member.
According to a thirty-ninth aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; first transfer means contacting the image bearing member to transfer a toner image on the surface thereof to an intermediate transfer member in the shape of an endless belt; and second transfer means contacting the intermediate transfer member to transfer a toner image on a surface thereof to a transfer substrate, wherein the second transfer means comprises an electrically conductive member including a cylindrical base body; and electrically conductive powder sealed inside of the cylindrical base body at a fill fraction in the range of from 20 to 95% of the inner volume thereof and the electrically conductive powder includes magnetic powder, the image forming apparatus further including: magnetic field forming means forming a magnetic field in which the electrically conductive powder is attracted to a support member provided at a position opposite the second transfer means on an inner peripheral section of the intermediate transfer member.